I was doing a logging of data for a battery life test for a laptop.

I randomly checked on the laptop and recorded the remaining battery% based on the laptops reading and the current time.

The upper part of this images is those data points.
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Later on I created the bottom data by multiplying by 1440 to get minutes and then subtracted 635 to get 0 as my starting point.

So my final 2 data points for my graph are the Battery % and the On Time.

When I graph them I get a line graph that looks like this:
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This is not my desired result :/ That sharp drop looks like there was a change in the battery life rate for some reason and its because I was gone for an hour at the park with the kids while the laptop ran. Excel is just mapping the data 1:1 and does not understand that the bottom axis is "time" and that I want it to take the data I gave it and map it over time to give me a average line based on all data. The kind of stuff they made us do all the time in school.

I feel like excel can do this just that I am not doing something right. I tried to go into the charts axis labeling options and tell it to use a preset interval of say 10 or 20 but it has no effect on the graph at all it just blanks out the axis labels.

So if you guys understand what I am trying to do, can you help me?

Thanks.